Windows: There are two options: MsysGit or running the compiled git under Cygwin. You can find more information in this github guide

Getting a github account (Optional)

Once you have git installed on your machine, you can get the code and start developing,
However, since the code is hosted at github, you can use more features if you sign up for github account.
This is completely optional but if you do sign up all other developers will be able to see (and review) the changes you have made.

Upload an ssh public key by clicking on 'account' after having logged in

Obtaining the source code

There are two ways of getting the code tree onto your machine. They're not that different, in fact both will result in a directory on your machine containing a full copy of the repository on your machine. However, if you have a github account, you can make your repository a public branch of the project. If you do so, other people will be able to easily review your code, make their own branches from it or merge it back to the trunk.

In fact you can change this later, using the .git/config file, but to make it easier I'll describe the two possibilities separately.

Forking biopython using a github account

If you are logged in to github, you can go to the Biopython repository page

Forking without a github account

This command creates a local copy of the biopython source on your machine. However, if you want other people to see your changes without github, you need to take care of publishing your branch yourself.

Making changes

Now you can make changes to your branch. Since your local branch is a full repository, you can commit your changes as often as you like. In fact, you should commit as often as possible, because smaller commits are much better to manage and document. Let us assume you've made changes to the file Bio/x.py. You need to add this file to your change-set:

git add Bio/x.py

and now you commit:

git commit -m "added feature Y in Bio.x"

Your commits in git are local, i.e. they affect only your working branch on your computer, and not the whole Biopython tree or even your fork on github. You don't need an internet connection to commit, so you can do it very often.

Once you think your changes are fine and should be reviewed by others, you can push your changes back to the github server:

git push origin

If you think you changes are worth including in the main Biopython distribution, then file an (enhancement) bug on Bugzilla, and include a link to your updated branch (i.e. your branch on github, or another public git server). You could also attach a patch on Bugzilla. If the changes are accepted, one of the Biopython developers will have to check this code into our CVS repository, and within the hour this should update the main Biopython branch on github.